The present invention relates to a storage battery provided with an electrolytic solution stirring device.
In storage batteries, an electrolytic solution is directly involved in a reaction resulting in the generation of electric power. Accordingly, it is well known that the capacity of a storage battery is greatly affected by the efficiency in utilization of the electrolytic solution in the storage battery as well as the efficiency in utilization of active matters of the electrode plates thereof.
In the case of a lead storage battery, the specific gravity of the electrolytic solution at the upper portion of the storage battery is lowered during the charge and discharge periods so that electrolytic solution which is high in specific gravity always remains at the lower portion of the storage battery.
To eliminate this disparity in density between portions of the solution, a gas is generated by overcharging so that the specific gravity of upper and lower portions of the electrolytic solution can be made uniform by the stirring action of the gas. In general, in the case where the storage battery is small in height, the specific gravity of the electrolytic solution can be made uniform relatively easily by overcharging. However, in the case where the storage battery used is large in height, like an electric car storage battery, generally, the specific gravity cannot be made uniform by some degree of overcharging. As a result, the electrolytic solution at the upper portions of the electrode plates always has a low specific gravity, so that the capacity of the battery is lowered. On the other hand, electrolytic solution having a high specific gravity and a strong oxidizing property always remains at the lower portions of the electrode plates, so that the lower end portions of the electrode plates are corroded to shorten their lifetime. For this reason, in general, overcharging is carried out whenever the storage battery is charged. As a result, not only is electric power wasted but the lifetime of the storage battery is shortened.
On the other hand, in the case of floor type storage batteries, various loads are connected to the storage batteries. Because some of those loads are not suited to a large voltage change due to charging, a constant-voltage charging system, in which the charging voltage is limited to a predetermined value, is often used. To solve those problems, uniform charging for a long time of 12 to 24 hours has been carried out. In the existing circumstances, however, the aforementioned problems cannot be solved because the uniform charging voltage is low.
In the case of a load-leveling large-capacity stationary battery, stirring is carried out periodically by forcing air into the battery from the outside. As a result, it has been confirmed that the battery lifetime may double depending on the existence of a stirring device. Further, the charge quantity during each charging generation can be reduced by 10%. As a result, consumption of water in the electrolytic solution due to overcharging can be reduced remarkably so that the water supply cycle is prolonged by five times, resulting in a remarkable reduction in maintenance cost.
However, the stirring device currently used requires compressor piping and the like, so that the overall cost increases and the use of such a stirring device is limited to batteries used for specific purposes.